This invention is related to flying model rockets, particularly of the type using a model rocket engine having an ejection charge for deployment of a recovery device, such as a parachute.
Model rockets are typically sold either assembled or in kit form. A typical model rocket uses a spiral wound paper tube for the body and balsa wood for the nose cone and fins. Although balsa is light, it is relatively fragile. The paper tubes are relatively inexpensive, but can limit the size of the rocket due to lack of strength.
People enjoy building model rockets, launching them, seeing them quickly ascend, reach their apex of flight and then return to earth, typically by deploying a parachute or streamer to slow the descent. A controlled, relatively slow descent is necessary to help prevent damage to the rocket and objects on the ground and to avoid injuring people and animals.
There are competing interests at work in the design of a model rocket. Many rockets are relatively small, under 2 feet in length, so they are light, for maximum height during flight, and so they can be transported and stored easily. Others are longer for better visibility during flight. Thus, although a 5 foot long rocket may be desirable from a visual standpoint, most rockets are much shorter so that they can be transported and stored more easily and to allow greater heights due to lower weight.
A common recovery system for model rockets uses a displaceable nose cone and a parachute. To deploy the parachute, this type of rocket uses a rocket engine having an ejection charge which ignites a short time after the boost charge is over and at about the time the model rocket is at its apex. The eJection charge produces a sudden surge of hot ejection gases inside the hollow rocket body to cause the parachute, housed in the body, to move forward dislodging the nose cone. However, there are a couple of problems with this recovery system. First, the rocket returns generally vertically and relatively rapidly because the rocket itself, being in a generally vertical orientation, provides little resistance to its descent. Enlarging the parachute to slow the descent may not be desirable due to the added weight. Another problem relates to protecting the paraohute. Wadding must be placed between the parachute and the source of the hot ejection gases to keep the parachute from being burned. If not done properly, the parachute can be partially or totally destroyed which can result in a faster than desired descent of the rocket. This can result in damage to the rocket, or in some cases, even injury to the user on the ground.